jetsfan101

Hey guys -

Just picked up a 2010 A6 3.0T. This is my 2nd C6. First one was a 2006. Fairly familiar with Audis, i have a Q7 now and most recently had a '06 A8.

When i got this one, it was leaking tiny amount of oil somewhere from the drivers side valve cover so i took it back to the dealer i got it from and they fixed it. Said they replaced 3 gaskets, valve cover was one of them. Did not specify the other two.

So i just got the car back and noticed a slight whiny squealing noise when i start the car cold. By cold i mean when it has been sitting 1+ hours.

At first i thought it was an idler pully or something, but then i played with the AC on/off and it turns out that the noise is gone when the AC if OFF. So it has something to do with the AC system. A pulley perhaps? Compressor? So here are the symptoms of the squealing:

When i start the car, the RPMs are at 1200. You hear a slight, but almost not noticeable constant whine noise. When the RPM drop down to operating 750-800, that noise is gone, BUT when i rev it up a bit, you hear the whine with it. It's most noticeable at 1000-1800 RPM. And it definitely sounds like something turning and squealing. Almost like lack of lubrication or something.

After few minutes, the sound is pretty much gone, but it comes back on the next cold start.

My main questions are:

1. What is the problem here?
2. When the mechanic fixed the oil leak by taking off valve cover, etc, could he have messed something up? Honestly, i don't think that noise was there before they did the work on the oil leak.
3. Is it something i need fixed now. I will try to reach out to the dealer again and imply that it is something they screwed up in the process, but i want to know what i am dealing with here.

Any feedback appreciated!!

jetsfan101

Having messed with it some more, i can now confirm that the squealing noise does not really go away, even after engine warms up. Just becomes i little quieter. So on low revs, you still hear a little whiny sound.

And overall, the engine just does not sound good idling when the AC is on. Sounds weak, like engine is thinking about stalling almost. With AC off, back to normal operation.


Has anyone had a similar issue? I would love to know what the problems may be

jetsfan101

It's most likely, AC compressor clutch thats located on the pulley. The noise comes on when the clutch engages( AC turns on). The pulley is rotating all the time with AC on or off, so that's likely not it.

Anyone have experience replacing that? How many hours labor would a mechanic charge for that? As far as i understand, you dont have to remove the AC compressor to get the pulley off

jetsfan101

Update: i replaced the AC compressor, but that did not fix the whine noise. The old compressor wasn't perfect you could hear the bearings inside rotating, so i guess it wasnt a total waste

I have diagnosed this down to either the accessory belt or the tensioner for that belt. The tensioner makes sence as the culprit of noise because when the AC compressor turns on, it puts more pressure on the belt and the tensioner. We shall see


Question: I found a basic worded DIY on how to replace the tensioner, but would love a detailed one with pics. Has anyone ever done this? What's the easiest way to access it, from top or bottom of engine? Etc